1. Field of the Invention
The present invention relates to a mechanism for use in a can opener that uses a quiet reversal mechanism that may be provided with a manual or automated drive mechanisms.
2. Related Background Art
U.S. Pat. No. 4,365,417 issued to Rosendahl on Dec. 28, 1982 and entitled “TIN OPENER” describes a can opener that uses a missing teeth structure at one end of travel of a cutter gear. The open position of the cutter lies at the end of a number of teeth of the cutter movement gear. In essence, a user turns a butterfly shaped actuator from a first, resting stopped position and in a direction of engagement that causes the cutter blade to move toward and engage the body of a can. At the point in which the cutter and the can, urged by a drive wheel, are closest, the drive gear encounters a “missing teeth” section of the cutter gear so that the drive gear can continue to turn the drive wheel and without having the cutter gear interfered with by the cutter gear's having stopped at the point where the cutter and the can are closest. The cutter engagement gear can be reversed to move the cutter wheel away from the drive wheel. The mechanism to assist this reversal is the use of a projection that extends outward towards a cover and is arranged to co-operate with a rubber cylinder situated within a circular ridge and an adjacent ridge and is intended to import a rotary movement to the tooth segment device. In essence, when the concave surface (missing teeth) is centrally opposite a pinion, the rotary movement tends to turn the tooth segment device (cutter gear) in such a way as to cause the teeth in the row of teeth (adjacent the section of missing teeth) to re-engage and cause the cutter gear to move the cutter away from the drive wheel.
The mechanisms to cause gear re-engagement from a position in which a drive gear opposes the “missing teeth” portion of another gear are many. Most involve a more complex method of re-starting the drive gear against the driven gear by detecting the reverse motion of the drive gear. In some designs a starter “clicking gear” is used to continually present the beginning gear of the reversal to the drive gear. Friction of an idler gear with respect to a driven gear can sometime be counted upon to get the driven gear going in a direction away from the “missing teeth” section of the driven gear. However both of these methods can greatly suffer. First, any “clicking” mechanism operates through continued wear and distracting noise. Second, the use of friction among gears in a highly lubricated environment can result in long terms changes in the ability of the driven gear to reverse. If a can opener becomes un-disengageable from a can or lid, the can opener becomes disposable or in the alternative a significant repair job is needed to free the can lid or can from the mechanism.
In the case of the Rosendahl device directly, there are several shortcomings that it has in terms of building a can opener that is utilizable in the safest and most secure way by the greatest number of people. The Rosendahl device has a butterfly drive handle which is a pair of oppositely oriented extensions that are each about one to two inches from the rotational center. The operation of the Rosendahl device requires significant dexterity, finger and thumb strength and wrist flexibility. Further, the use of a butterfly actuator involves a series of partial turns interrupted by stopping and thence further partial turns. High dexterity and strength is required. A further undesired by-product of this method of operation is the necessity to grasp the opener with one hand, periodically operate the opener with the other hand, while putting some downward pressure on the can with both hands in order to stabilize the food contents during the opening activity. To prevent spillage, the user orients the opener and the can on a flat surface and operates it in an awkward position sacrificing user comfort in exchange for a necessity to use the table as a stabilizing reference point. A user would not normally think of supporting the can to be opened with the hand supporting the bulk of the opener as the motion would be too much of a jerking motion that would cause a mess. This is because the manual force necessary to open the can is significant, as well as periodically occurring.
The Rosendahl device generally must be made of a metallic construction. One end of the toothed gear set on the cutter wheel movement gear is made up of a blocking tooth. Once the user reaches the non-operating end of the tooth segment device (toothed gear set on the cutter wheel movement gear) it cannot be rotated further by means of its pinion drive gear. Only a metal construction would have the force of hold against a user “trying” to continue movement of the pinion gear in the opposite direction. In essence one of the stronger failure modes of the Rosendahl devices occurs at the non-working end of its operational range. In a good can opener, the maximum forces should be put to work forming a nip in the can or in opening the can, not in providing strength at a non-operating end point of the opening cycle.
Another important aspect in which the Rosendahl device falls short is the requirement generally for significant strength on the part of the person opening the can. The fact that the Rosendahl device is required to be made of metal and have strength to defeat damage from turning it in the direction of the non-operating position. Requiring only enough force to make the nip and open the can might also have caused Rosendahl to have considered persons of limited strength and their need to utilize a can opener that they could operate. If the Rosendahl mechanism were optimized, then a motorized version of the design might have been practically possible. However, the single, blind ended cycle of opening would have caused Rosendahl to have included more complex stopping sensors to insure that any motorized force would not challenge the return to the non-operating position. Any motorization of this type of end point can set the mechanics of motorization against the mechanics of operation and create destruction of both. Put another way, the simple provision of the mechanism of Rosendahl into a heavy motorized housing would either have created a significant cost in sensors, electronics to precisely control the cycle, or might have ended with the motorization gearing and the operational gearing destructively fighting with each other.
What is therefore needed is a mechanism that can provide a mechanically advantaged engagement of the cutter wheel toward the can to form the nip, followed by continuous operation until the can is open. A needed can opener of this type, in order to be available in large quantity at an inexpensive price in order to facilitate its purchase as a perfunctory and useful item, should be amenable to an inexpensive construction while having a long lasting high quality mechanism. The mechanism should not make any discernible noise and should operate consistently regardless of the amount of lubrication within the gear mechanism. Most importantly, a needed can opener mechanism should facilitate use of a can opener into which it is placed by providing ease of manual operation in the case of a manual opener, and low energy consumption/long battery service in the case when the needed can opener mechanism is motorized.